Telecommunication services are offered via Public Land Mobile Networks (PLMNs) to a user equipment (UE). A user may operate the UE. A PLMN is typically subdivided into an access network, a core network and an Internet Protocol (IP) Multimedia Subsystem (IMS). Services are typically provided by a user's home network. When the user is using a non-home network, the visited network may have a relation with the user's home network. Some communications transmitted by the UE are communicated all the way back to the home network, via the visited network.
These communications may take different routes, travel through different network elements based on for example the type of relationship between the home network and the visited network, or based on the technology of the networks. For example, a 5th Generation (5G) core network has different network elements compared to an Enhanced Packet Core (EPC) network.
The IMS may comprise a Proxy Call Session Control Function (P-CSCF). The EPC may comprise a Mobility Management Entity (MME) or a Packet Data Network (PDN) Gateway (GW), and the 5G Core Network (CN) may comprise an Access and Mobility Management Function (AMF) or User Plane Function (UPF). A CN supports the IMS.
Networks may offer a Circuit Switched (CS) domain, where traditionally voice calls and emergency calls are handled, or a Packet Switched (PS) domain, offering PS services including access to the IMS.
The PS domain supports emergency services via the IMS. A UE may support accessing one or both of the CS domain and PS domain. A UE able to access the PS domain may also support accessing the IMS.
When an emergency call attempt is not detected as such by the UE on the PS domain, the UE may be redirected. Several forms of redirection exist and some of them may occur in a sequence. When an undetected emergency call attempt is redirected, the UE needs to retry the call using emergency procedures. The redirection and retrying is time consuming and may cause the user to terminate the call attempt. These problems are only exacerbated if the user subsequently retries the emergency call.